Process for producing integral skin polyurethane foam

Abstract

Integral skin polymethane foams can be produced in a short time by impingement mixing a solution comprising polyols containing as an essential component a polyol derived from aromatic amine, a blowing agent and a special catalyst of tertiary amine salt having a hetero ring in the molecule, with a solution comprising one or more polyisocyanates, followed by injection into a closed mold and foaming and curing therein.

What is claimed is: 
     
       1. A process for producing an integral skin polyurethane foam which comprises: impingement mixing at least two solutions, one of which comprises polyols containing: (a) at least one polyol of an alkylene oxide adduct of an aromatic amine having the formula: ##STR9##  wherein R is hydrogen or a lower alkyl group; R' is an aromatic residue; and m, n, p and q are independently an integer of 1 or more, in an amount of 20 to 80 parts by weight,   (b) at least one polyol of an alkylene oxide adduct of aliphatic amine in an amount of 5 to 70 parts by weight, and   (c) at least one polyether polyol or polyester polyol in an amount of 0 to 50 parts by weight, a blowing agent and as a catalyst at least one tertiary amine salt having a hetero ring in the molecule, and another solution of which comprises one or more polyisocyanates in an amount of 0.95/1 to 1.30/1 in terms of isocyanate index,      injecting the resulting impingement mixed solution into a closed mold, and    conducting foaming and curing in the closed mold.     
     
     
       2. A process according to claim 1, wherein in the formula (I) R is hydrogen or a methyl group, R' is ##STR10## m, n, p, and q are independently an integer of 1 to 10. 
     
     
       3. A process according to claim 1, wherein the catalyst is at least one acid salt, phenol salt or cresol salt of a diazabicyclo-alkane or an imidazole. 
     
     
       4. A process according to claim 3, wherein the catalyst is a phenol salt of 1,8-diazabicyclo[5,4,0]-undecene-7. 
     
     
       5. A process according to claim 1, wherein the polyisocyanate is one represented by the formula: ##STR11## wherein l is 0.3 to 0.8. 
     
     
       6. A process according to claim 1, wherein the polyols have an average hydroxyl value of 380 to 760 KOH mg/g. 
     
     
       7. A process according to claim 1, wherein the blowing agent is a low-boiling halogenated hydrocarbon. 
     
     
       8. A process according to claim 1, wherein the closed mold has a mold temperature of 45° to 80° C. 
     
     
       9. A process according to claim 8, wherein the closed mold has a mold temperature of 55° to 80° C. 
     
     
       10. A process according to claim 1, wherein the solutions are three solutions, one of which comprises polyols containing as an essential component at least one polyol of an alkylene oxide adduct of an aromatic amine having the formula (I), a blowing agent and as a catalyst at least one tertiary amine salt having a hetero ring in the molecule, another of which comprises one or more polyisocyanates and the rest of which comprises at least one component selected from the group consisting of pigments, dyes, and blowing agents. 
     
     
       11. A process for producing an integral skin polyurethane foam which comprises: impingement mixing at least two solutions, with (a) one of said at least two solutions comprising (1) polyols containing at least one polyol of an alkylene oxide adduct of an aromatic amine having the formula: ##STR12##  wherein R is hydrogen or a lower alkyl group; R' is an aromatic residue; and m, n, p and q are independently an integer of 1 or more; (2) a blowing agent; and (3) a catalyst for producing the polyurethane comprising at least one tertiary amine salt having a hetero ring in the molecule, and (b) another of said at least two solutions comprising one or more polyisocyanates,   injecting the resulting impingement mixed solution into a closed mold, and   conducting foaming and curing in the closed mold to provide a polyurethane foam having an integral skin.   
     
     
       12. A process according to claim 11, wherein the polyisocyanate is used in an amount of 0.95/1 to 1.30/1 in terms of isocyanate index. 
     
     
       13. A process according to claim 11 or 12, wherein R' is: ##STR13## R is hydrogen or lower alkyl group, and m, n, p and q are independently integers of 1 to 10. 
     
     
       14. A process according to claim 13, wherein said lower alkyl group has 1-5 carbon atoms. 
     
     
       15. A process according to claim 11, wherein said at least one polyol is selected from the group consisting of ethylene oxide or propylene oxide adduct of diaminodiphenylmethane, ethylene oxide or propylene oxide adduct of tolyenediamine, and ethylene oxide or propylene oxide adduct of xylylenediamine. 
     
     
       16. A process according to claim 11, wherein said polyols have an average hydroxyl value of 380 to 760 KOH mg/g. 
     
     
       17. A process according to claim 11, wherein the hetero ring of the catalyst is a nitrogen-containing ring. 
     
     
       18. A process according to claim 17, wherein the at least one tertiary amine salt includes a salt of a tertiary amine selected from the group consisting of diazobicyclo-alkenes and imidazoles. 
     
     
       19. A process according to claim 11, wherein the at least one tertiary amine salt is formed by adding to a tertiary amine formic acid, oxalic acid, propionic acid, phosphonic acid, 2-ethylhexoic acid, nitric acid, hydrochloric acid, or a compound having a phenolic hydroxyl group. 
     
     
       20. A process according to claim 19, wherein said compound having a phenolic hydroxyl group is phenol or cresol. 
     
     
       21. A process according to claim 11, wherein said at least one tertiary amine salt is used in an amount of 0.2 to 10 parts by weight per 100 parts by weight of said polyols. 
     
     
       22. A process according to claim 11, wherein said polyols also include alkylene oxide adducts of aliphatic amines.